This work is in the public domain because it was published in the United States between 1923 and 1963 and although there may or may not have been a copyright notice, the copyright was not renewed. Unless its author has been dead for the required period, it is copyrighted in the countries or areas that do not apply the rule of the shorter term for US works, such as Canada (50 pma), Mainland China (50 pma, not Hong Kong or Macao), Germany (70 pma), Mexico (100 pma), Switzerland (70 pma), and other countries with individual treaties. See Commons:Hirtle chart for further explanation.